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I know, there are variables, but approximately what should be the difference in temperature between return air and register air? I have a brand new system and it is running almost constantly on hot days. The installer came back and checked the charge but that was in late January at it was barely 70 degrees outside. Should I insist they come back again? My difference in temp from return to register is 15 degrees. I measured the register air at a register halfway down the trunk line in order to get the average when taking heat gain from the attic into account. Thanks in advance.

temp difference

the temp diff sounds right it is usally about 10 to 15 degrees difference.it sounds to me like you have a problem with your insulation or something letting your air escape or allowing the heat get in and also where is your thermostat located. it should be in a central spot or close to the return air to get atrue reading and make sure its not in a spot where the sun is on it.also do you have a return at the highest point in the house that would make a difference.

Thanks for the reply coolcray, I actually have two ceiling returns, one is directly above the thermostat. My house very old and I'm in the process of restoring it. Currently the only insulation is in the attic. I know more insulation will help, but the heat worked very well. If the problem is purely the lack of insulation I'll just have to grin and bear the utility bill unitl I get around to adding more. I have added an attic fan to help reduce heat transfer to the ductwork. Someone in another forum suggested addin additional insulation to the ducts. My main concern is that if something is wrong with the unit I want to get it right before too much time passes. I'm just about to the point of hanging blankets over the windows when I think of the electric meter spinning away!

air temp

if all the ducts are insulated with duct wrap and the house is old thats all you can do the heat from out side is radiating right through the walls and any air gaps it can get through. the unit is right on with the temp of the air. sometimes the attic fan will cause a air pull through the house and pull the heat in as well as venting the attic space. you want to make sure your attic is sealed from the house and not pulling out the ac and pulling in the heat at the same time

Thanks again coolcray. I guess I'll get some cans of spray foam and go to work plugging any gaps in the attic. I have two windows up there open, but I guess there could still be some air pulling through around ceiling fixtures and stuff.

Cem, I have white plantation blinds on most of the windows, but there is one room with BIG windows that don't have blinds yet. I might have to improvise something to cover those windows with for the time being. Thanks for the input.

air temp

if you have open windows up there that should be plenty of intake air for the fan to pull from. i think i would consentrate on making sure that your attic opening to the house is sealed and try some window coverings that will deflect the sun and heat

look at the hole in the wall where the thermostat wires come out behind the stat. Is the hole sealed, filled with caulk or something? If not it should be, hot air can be cruising through your wall like an chimney and right into your thermostat.

The high temperature has approached 95 for the last week, unusually hot for the area. I plugged up th ehole behind the thermostat when I changed it to a programable one (which cut the natural gas bill in half)